exactly 32 - Control of cardiac performance- self-control. Cardiac energetic and functions of the heart. Neural extrinsic regulation of Cardiac Performance- Sympathetic and parasympathetic effects. Humeral factors affecting cardiac performance.

sections

control of cardiac performance

frank-starlings law of heart

self control of heart

sympathetic and parasympathetic control

functions of heart

control of cardiac performance

• cardiac performance in relation to the volume of blood pumped by the heart per beat, is controlled by the autonomic nervous system and also through intrinsic – self control intrinsic control

• The hearts activity refers to its ability to adapt to changes to the loads of inflowing blood. This is based on the Frank-Starling law of the heart

• The law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume) when all other factors remain constant

• the extra blood stretches the muscles more therefore the contraction is greater, it increases preload- the degree of stretching of the walls of the heart chambers- ventricle, and so the force of contraction will be greater. The heart rate itself is controlled by the number of contractions of the heart per minute- beats per minute.

frank-starlings law of heart

The law states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume) when all other factors remain constant

self control of heart

The sinoatrial node generates action potentials constantly which results in cardiac muscle contraction. The faster the rate at which action potentials are generated, the faster the heart rate.

sympathetic and parasympathetic control

• Autonomic nervous system has two branches- parasympathetic and sympathetic. They both effect the cardiac activity- heart rate, contractivity, exitability etc.

• The ANS has 5 effects on the heart:

  • Inotropic: strength of contraction

  • Bathmotropic: excitation of cardiomyocyte

  • Chronotropic: frequency of contraction

  • Dromotropic: conduction of impulses through cardiomyocytes

  • Tonotropic: tone of cardiomyocyte

• Sympathetic effect: All the above five effects increase

• Parasympathetic effect: All the above five effects decrease

• Kidney: sympathetic effect increases RENIN excretion

functions of heart

• oxygen to other parts of body via pulmonary circulation

• system circulation

sections

neural extrinsic regulation of cardiac performance - sympathetic

neural extrinsic regulation of cardiac performance - parasympathetic

parasympathetic nerves

sympathetic effects

humoral factors affecting cardiac performance

neural extrinsic regulation of cardiac performance - sympathetic

Sympathetic nerves liberate norepinephrine which stimulates the heart increasing its rate and sense of contraction

Both sets of nerve supply the SAN and AVN and affect the heart rate by their influence in the sinoatrial node (pacemaker)

neural extrinsic regulation of cardiac performance - parasympathetic

Parasympathetic nerves- liberate acetylcholine which inhibits the heart- slowing down its rate.

Both sets of nerve supply the SAN and AVN and affect the heart rate by their influence in the sinoatrial node (pacemaker)

parasympathetic nerves

• The vagus nerve is the parasympathetic nerve that innervates the SAN.

• It secretes neurotransmitter acetylcholine which then binds to muscorinic receptors in the SA-node cells.

• Parasympathetic- atria

• Activation of SNS -atria and ventricle

• Heart (Beta) The ANS has 5 effects on the heart:

  • Inotropic: strength of contraction

  • Bathmotropic: excitation of cardiomyocyte

  • Chronotropic: frequency of contraction

  • Dromotropic: conduction of impulses through cardiomyocytes

  • Tonotropic: tone of cardiomyocyte

Parasympathetic effect: All the above five effects decrease

during exercise emotional stress dehydration causes vasoconstriction of arteries and veins mediated by alpha adrenoreceptors and increase heart rate contractile rate of relaxation and conduction velocity by beta 1 adrenoreceptors.

sympathetic effects

• Heart (Beta) The ANS has 5 effects on the heart:

  • Inotropic: strength of contraction

  • Bathmotropic: excitation of cardiomyocyte

  • Chronotropic: frequency of contraction

  • Dromotropic: conduction of impulses through cardiomyocytes

  • Tonotropic: tone of cardiomyocyte

Sympathetic effect: All the above five effects increase

during exercise emotional stress dehydration causes vasoconstriction of arteries and veins mediated by alpha adrenoreceptors and increase heart rate contractile rate of relaxation and conduction velocity by beta 1 adrenoreceptors.

humoral factors affecting cardiac performance

• Hormones which increase the heart rate include thyroxine – T4, triiodothyrine-T3 which are secreted by the thyroid gland

• nerve stimulation leads to the release of epinephrine- adrenaline which binds to receptors on the SAN resulting in an increase in the heart rate